A thought on the teaching style: even someone like Kuroda Testuszan who was born into a family with a tradition of jujutsu, did not begin to comprehend the power of the kata until well into his thirties. His father and grandfather used to say that their ideal is to leave behind the kata as an inheritance. If the kata remained in existence in some form, then someone or other with the right mind would be able to see its meaning and train themselves. If that could happen, they would have succeeded in their duty. There was never thought to explicitly teaching all the details to anyone, althought the number of hints might be greater or lesser. Specifically, Kuroda states that with respect to the kata, his grandfather only ever used to say one or two things repeatedly, and when Kuroda finally started to grasp the truth behind the kata, he realized that what he had been told was true, but not in the sense that he had though before. So, as far as I am concerned, the teaching tradition in Japan and possibly the rest of Asia simply does not premise a good practitioner actively teaching students anything. In a Western sense that could be interpreted as "purposely showing only in order to maintain an edge" but that is not necessarily the case.